cygthread: suspend thread before terminating.

It seems SuspendThread makes sure the thread is "booted" from emulation
before it is suspended.  Hopefully this means it won't be holding any
locks or otherwise leave emulation in a bad state when it's terminated.

winsup/cygwin/cygthread.cc

@@ -302,6 +302,13 @@ cygthread::terminate_thread ()
   if (!inuse)
     goto force_notterminated;
 
+  if (_my_tls._ctinfo != this)
+    {
+      CONTEXT context;
+      SuspendThread(h);
+      GetThreadContext(h, &context);
+    }
+
   TerminateThread (h, 0);
   WaitForSingleObject (h, INFINITE);
   CloseHandle (h);